A semiconductor manufacturing process includes a photoresist process in which a resist is coated onto the surface of a semiconductor wafer (hereinafter referred to simply as a wafer), exposed in a predetermined pattern, and then developed to form a resist pattern. Such a process is generally performed by a system in which a coating-and-developing apparatus for coating and developing a resist is connected to an exposure apparatus.
The developing apparatus disclosed in JP2001-327909A includes a developer nozzle 11 having a slit formed in its underside and extending in the longitudinal direction thereof, as shown in FIG. 16. This slit acts as an ejection port and has a length equal to or larger than the diameter of the wafer (W). The developer nozzle 11 moves from one end to the opposite end of the wafer W, which is held still in a horizontal attitude by a spin chuck 1, while ejecting the developing solution through the ejection port facing the wafer W, thereby to deliver a developing solution to the entire surface of the wafer W.
With reference to FIG. 17, there will now be briefly described a series of steps for developing a wafer W by using the above developing apparatus. First, a wafer W with an exposed resist film on its top surface is held in a horizontal attitude on the spin chuck 1. Then, as described above, the developer nozzle 11 is moved from one end of the surface of the wafer W to the opposite end of the same to apply a developing solution D to the surface of the wafer W, as shown in FIG. 17(a). Upon reaching the opposite end, the developer nozzle 11 stops the ejection of the developing solution D and is moved to its retracted position, as shown in FIG. 17(b). Then, the wafer W with the developing solution D accumulated on its surface is left for a predetermined period of time to cause “stationary development” (of the resist), as shown in FIG. 17(c). After that, a rinse liquid nozzle 12 is positioned above the center portion of the wafer W, as shown in FIG. 17(d), and a rinse liquid R (for example, deionized water) is delivered to the center portion of the wafer W through the rinse liquid nozzle 12 while rotating the wafer W around its vertical axis by using the spin chuck 1, as shown in FIG. 17(e). Then, the supply of the rinse liquid is stopped, the rinse liquid nozzle 12 is moved to its retracted position, and the wafer W is rotated at high speed to spin-dry it, as shown in FIG. 17(f), completing the developing process. In this case, the period of time from the point of time when the developer nozzle 11 begins to eject the developing solution to the point of time the supply of the rinse liquid begins, in other words, the period during which the developing solution actually reacts with the resist due to their contact may be regarded as the actual developing time. The developing time is typically 60 seconds in the conventional art.
However, the above developing method suffers from the following problem. Generally, components 13 of the resist 14 dissolved in the developing solution D begin to diffuse from the surface layer of the resist 14 due to the concentration gradient, as schematically shown in FIG. 18, 18-20 seconds after the developing solution D is delivered, even though this diffusion starting time point somewhat varies depending on the type of resist. These dissolved resist components 13 move in a random manner, leading non-uniform dissolution of the resist. In order to avoid the influence of the non-uniform diffusion of the dissolved resist components 13, the rinse liquid may be ejected early to remove the developing solution containing the dissolved components 13 early. In this case, however, it is not possible to ensure a developing time long enough to develop a resist having a low dissolution rate. As a result, the bottom portions 14b of the resist may remain undeveloped (which is called “under-development”), for example.